1. Technical Field
The present device relates to the technical field of welding and, more particularly, to inert-gas shielded welding.
2. State of the Art
Until recently, welds were produced entirely manually by an operator who held the metal welding wire in one hand and the torch providing the power needed to melt the wire in the other hand.
There later appeared portable devices that reproduce the movement of the operator""s hand which held the wire. Such known devices are disclosed, for example, in patent FR 2 723 330.
The semi-automatic welding device described in that patent makes it possible, firstly, to free up the operator""s hand holding the wire and, secondly, to provide a uniform overall feed movement of the filler wire at the same time as a combined reciprocating movement of the filler wire.
Such a device has allowed the time spent by an operator welding, and likewise the quality of work performed, to be substantially increased since the filler wire feed is more uniform. In addition, the work is carried out more quickly and thus the time spent heating the metal workpieces to be welded is reduced, consequently reducing the risk of deforming the workpieces that it is desired to weld and therefore reducing raw material wastage and saving time.
All these advantages have the result that the costs associated with the welding operations are reduced, owing to a substantial increase in productivity and less material wasted.
The movement of filler wire providing all these advantages is obtained in that device of the prior art by means of two motor drives for the filler wire.
These two motor drives are independent of each other and controlled by independent controls, one allowing the continuous feed speed of the filler wire to be varied by means of a first motor and the other allowing the frequency of the reciprocating movement to be varied by means of a second motor.
The function of the first motor drive is to impart to the filler wire a uniform feed movement so that the welding torch is uniformly supplied with filler wire.
The function of the second motor drive is to impart to the filler wire a forward and backward or reciprocating movement of the filler wire (stepwise movement), thereby reliably reproducing the movement of the operator""s hand applied to the wire.
To fulfill these functions, namely the continuous feed movement of the filler wire and the reciprocating movement, the device according to the prior art comprises filler wire drive means which are motors.
These motors are typically of the low-voltage type and actuate one or more means for transferring the rotational movement to drive rollers on which the filler wire rests, the wire being applied against the drive rollers by means of a backing rollers, which allows the filler wire to be driven and continuously fed.
The drive rollers which are present on a support plate are themselves given a reciprocating movement by means suitable for imparting a reciprocating movement to said support plate. The combined two movements give the filler wire a movement identical to that which a skilled welder would impart to a filler wire used for the welding.
The second motor may be coupled directly to a cam having at least two bearing points, or to a support coupled to a connecting rod which acts on the support plate which also carries the rollers that provide continuous feed of the filler wire.
However, this semiautomatic welding device of the prior art has a major drawback in that such devices require the operator to make two separate adjustments. The first adjustment is adjustment of the continuous feed or rate of unspooling of the filler wire. The second adjustment is adjustment of the speed of the reciprocating movement of the filler wire, which depends on the amount of power delivered to the torch and therefore on the rate of melting of the filler wire, while taking into account the amplitude of the reciprocating movement of the filler wire. These two adjustments must be performed simultaneously, requiring the operator to use both hands at the same time to act on the two adjustment means. This therefore prevents him from immediately checking in situ and in visu whether the adjustment that he has made is correct, according to the nature of the weld to be produced and the characteristics of the filler wire used for the welding.
This is because different kinds of filler wire can be used, depending on the nature of the workpieces to be welded. It will be preferred to have relatively bulky weld droplets produced at a relatively high frequency. It would also be necessary to find a good compromise between the number of droplets that it is desired to deposit per unit length and the type of welding to be carried out.
For proper adjustment, the operator must therefore find a compromise between the fixed amount of power supplied to the torch, the frequency and amplitude of the reciprocating movement of the filler wire and the continuous feed speed or rate of unspooling of the filler wire from the spool.
Adjustment is made more difficult by the fact that the filler wire may have a variable thickness and be made of a different metal or metal alloy depending on its application. The use of metals or alloys of different type means that different amounts of power must be supplied to melt them.
This operation of adjusting the parameters is irksome and meticulous, especially if the operator is required to make many adjustment operations over the course of the time he is working on many different workpieces of different type.
To make the correct adjustment, the operator must have the proper know-how. This requires having a good knowledge of the various types of welds and especially the number of droplets that should be deposited in order to obtain a suitable weld and one which is appropriate to the type or style of workpieces to be welded.
Thus, to obtain the desired weld with the correct characteristics, a fine and appropriate adjustment is required.
This is why, in the devices of the prior art, in particular in the device described in patent FR 2 723 330, two separate adjustment means have been retained so as to maintain the freedom of separately acting and controlling, on the one hand, the wire pay-out speed and, on the other hand, the speed of the reciprocating movement.
These devices of the prior art have thus allowed the freedom of acting separately on these two parameters to be preserved, so as always to have the best possible weld quality. Despite the difficulties in using these devices of the prior art, its seems that the profession accepts these devices so as to preserve the accuracy of adjustment.
The drawback with such welding devices is that, for correct efficiency, they must be handled by a relatively skilled operator. These devices therefore do not completely dispense with skilled labor, which presents the drawback of increased labor costs.
It is therefore an object of the invention to provide a welding device that retains the essential advantages afforded by the prior art devices yet solves the crucial problem of the difficulty of adjusting and maintaining a constant welding quality.
It is another object of the present invention to provide a welding device with easy-to-use operator control of the kinematic parameters (e.g., continuous feed movement and reciprocating movement) of filler wire embodied therein.
It is a further object of the present invention to provide a welding device with a single adjustment that controls the kinematic parameters (e.g., continuous feed movement and reciprocating feed movement) of the filler wire embodied therein.
It is a further object of the present invention to provide a welding device with a single motor that provides desired kinematic movement (e.g., continuous feed movement and reciprocating feed movement) of the filler wire embodied therein.
In accord with these objects, which will be discussed in detail below, an improved welding device is provided that includes a casing, a power supply unit, a carriage for continuous delivery of filler wire, conduit that carries filler wire to an outlet nozzle, and at least one motor. First wire drive means, mechanically coupled to the motor(s), imparts reciprocating movement to filler wire that is carried in the conduit to the outlet nozzle. Second wire drive means, mechanically coupled to the motor(s), imparts continuous movement to filler wire that is carried in the conduit to the outlet nozzle. A single controller is adapted to control the motor(s) to obtain desired kinematic characteristics of movement of the filler wire, preferably giving the filler wire the same kinematics as a welder""s hand. The motor parameters and corresponding kinematic characteristics of the filler wire is adjusted by the single controller in response to a single operator actuated adjustment means. Preferably, a single motor is mechanically coupled to the first and second wire drive means to impart desired kinematic movement to the filler wire during operation of the single motor. Such a welding device coordinates and synchronizes continuous movement and reciprocating movement of the filler wire and makes adjustment of such movements very easy for the operator. Moreover, the device allows a very high quality of welding to be maintained, even if the device is used by an unskilled operator.
In addition, the single controller can be adapted to automatically control the amount of power delivered to device""s torch for melting the filler wire in addition to the kinematic parameters of the filler wire. These kinematic parameters and torch power levels may be calculated based upon characteristic values of the filler wire and of the workpieces to be welded (which are input thereto), such as the diameter of the wire, the nature of the metal of which the wire is made, the thickness and nature of the workpieces to be welded.
In addition, thanks to its design, the device makes it possible to devise welding sets taking up less space than the devices of the prior art. This smaller size allows access to very confined places which would be inaccessible using the devices of the prior art, for example in shipbuilding.
Moreover, owing to its limited number of components, its manufacturing cost is low as the complexity of assembly is less. Manufacture is therefore more rapid. In addition, since there are a small number of parts, the purchase cost of the components is also low, the more so as these components may be readily available on the market.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.